Step 1 :
After factoring out $ 5 $ we have:
$$ 5x^{2}+20x-15 = 5 ( x^{2}+4x-3 ) $$Step 2 :
Step 2: Identify constants $ \color{blue}{ b }$ and $\color{red}{ c }$. ( $ \color{blue}{ b }$ is a number in front of the $ x $ term and $ \color{red}{ c } $ is a constant). In our case:
$$ \color{blue}{ b = 4 } ~ \text{ and } ~ \color{red}{ c = -3 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 4 } $ and multiply to $ \color{red}{ -3 } $.
Step 3: Find out pairs of numbers with a product of $\color{red}{ c = -3 }$.
PRODUCT = -3 | |
-1 3 | 1 -3 |
Step 4: Because none of these pairs will give us a sum of $ \color{blue}{ 4 }$, we conclude the polynomial cannot be factored.